Airgialla

Airgialla, also known as Oriel, was an Irish kingdom which existed in northern Ireland from 331 to 1585. The kingdom was founded by the Three Collas, who conqured central Ulster from Ulaid at the 331 AD battle of Achadh Leithdherig. Airgialla was a confederation of nine minor kingdoms who paid suzerainty to an over-king, and its main towns were Armagh and Clogher. During the 6th century, it decreased in power due to the encroachments of Ailech and Mide, and, in 827, they became vassals of Ailech. Airgialla was confined to County Monaghan after the Norman invasion of Ireland, only to be conquered during the Tudor conquest of Ireland.